diff --git a/core/trie.go b/core/trie.go
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+++ b/core/trie.go
@@ -0,0 +1,154 @@
+package core
+
+import (
+	"math/big"
+)
+
+// Trie is a Ethereum Merkle Patricia trie.
+type Trie interface {
+	// GetKey returns the sha3 preimage of a hashed key that was previously used
+	// to store a value.
+	//
+	// TODO(fjl): remove this when StateTrie is removed
+	GetKey([]byte) []byte
+
+	// TryGet returns the value for key stored in the trie. The value bytes must
+	// not be modified by the caller. If a node was not found in the database, a
+	// trie.MissingNodeError is returned.
+	TryGet(key []byte) ([]byte, error)
+
+	// TryGetAccount abstracts an account read from the trie. It retrieves the
+	// account blob from the trie with provided account address and decodes it
+	// with associated decoding algorithm. If the specified account is not in
+	// the trie, nil will be returned. If the trie is corrupted(e.g. some nodes
+	// are missing or the account blob is incorrect for decoding), an error will
+	// be returned.
+	TryGetAccount(address Address) (*StateAccount, error)
+
+
+	// TryUpdate associates key with value in the trie. If value has length zero, any
+	// existing value is deleted from the trie. The value bytes must not be modified
+	// by the caller while they are stored in the trie. If a node was not found in the
+	// database, a trie.MissingNodeError is returned.
+	// TryUpdate(key, value []byte) error
+
+	// TryUpdateAccount abstracts an account write to the trie. It encodes the
+	// provided account object with associated algorithm and then updates it
+	// in the trie with provided address.
+	// TryUpdateAccount(address Address, account *StateAccount) error
+
+	// TryDelete removes any existing value for key from the trie. If a node was not
+	// found in the database, a trie.MissingNodeError is returned.
+	// TryDelete(key []byte) error
+
+	// TryDeleteAccount abstracts an account deletion from the trie.
+	// TryDeleteAccount(address Address) error
+
+	// Hash returns the root hash of the trie. It does not write to the database and
+	// can be used even if the trie doesn't have one.
+	Hash() Hash
+
+	// Commit collects all dirty nodes in the trie and replace them with the
+	// corresponding node hash. All collected nodes(including dirty leaves if
+	// collectLeaf is true) will be encapsulated into a nodeset for return.
+	// The returned nodeset can be nil if the trie is clean(nothing to commit).
+	// Once the trie is committed, it's not usable anymore. A new trie must
+	// be created with new root and updated trie database for following usage
+	// Commit(collectLeaf bool) (Hash, *NodeSet)
+
+	// NodeIterator returns an iterator that returns nodes of the trie. Iteration
+	// starts at the key after the given start key.
+	NodeIterator(startKey []byte) NodeIterator
+
+	// Prove constructs a Merkle proof for key. The result contains all encoded nodes
+	// on the path to the value at key. The value itself is also included in the last
+	// node and can be retrieved by verifying the proof.
+	//
+	// If the trie does not contain a value for key, the returned proof contains all
+	// nodes of the longest existing prefix of the key (at least the root), ending
+	// with the node that proves the absence of the key.
+	Prove(key []byte, fromLevel uint, proofDb KeyValueWriter) error
+}
+
+// StateAccount is the Ethereum consensus representation of accounts.
+// These objects are stored in the main account trie.
+type StateAccount struct {
+	Nonce    uint64
+	Balance  *big.Int
+	Root     Hash // merkle root of the storage trie
+	CodeHash []byte
+}
+
+// NodeIterator is an iterator to traverse the trie pre-order.
+type NodeIterator interface {
+	// Next moves the iterator to the next node. If the parameter is false, any child
+	// nodes will be skipped.
+	Next(bool) bool
+
+	// Error returns the error status of the iterator.
+	Error() error
+
+	// Hash returns the hash of the current node.
+	Hash() Hash
+
+	// Parent returns the hash of the parent of the current node. The hash may be the one
+	// grandparent if the immediate parent is an internal node with no hash.
+	Parent() Hash
+
+	// Path returns the hex-encoded path to the current node.
+	// Callers must not retain references to the return value after calling Next.
+	// For leaf nodes, the last element of the path is the 'terminator symbol' 0x10.
+	Path() []byte
+
+	// NodeBlob returns the rlp-encoded value of the current iterated node.
+	// If the node is an embedded node in its parent, nil is returned then.
+	NodeBlob() []byte
+
+	// Leaf returns true iff the current node is a leaf node.
+	Leaf() bool
+
+	// LeafKey returns the key of the leaf. The method panics if the iterator is not
+	// positioned at a leaf. Callers must not retain references to the value after
+	// calling Next.
+	LeafKey() []byte
+
+	// LeafBlob returns the content of the leaf. The method panics if the iterator
+	// is not positioned at a leaf. Callers must not retain references to the value
+	// after calling Next.
+	LeafBlob() []byte
+
+	// LeafProof returns the Merkle proof of the leaf. The method panics if the
+	// iterator is not positioned at a leaf. Callers must not retain references
+	// to the value after calling Next.
+	LeafProof() [][]byte
+
+	// AddResolver sets a node resolver to use for looking up trie nodes before
+	// reaching into the real persistent layer.
+	//
+	// This is not required for normal operation, rather is an optimization for
+	// cases where trie nodes can be recovered from some external mechanism without
+	// reading from disk. In those cases, this resolver allows short circuiting
+	// accesses and returning them from memory.
+	//
+	// Before adding a similar mechanism to any other place in Geth, consider
+	// making trie.Database an interface and wrapping at that level. It's a huge
+	// refactor, but it could be worth it if another occurrence arises.
+	AddResolver(NodeResolver)
+}
+
+// NodeResolver is used for looking up trie nodes before reaching into the real
+// persistent layer. This is not mandatory, rather is an optimization for cases
+// where trie nodes can be recovered from some external mechanism without reading
+// from disk. In those cases, this resolver allows short circuiting accesses and
+// returning them from memory.
+type NodeResolver func(owner Hash, path []byte, hash Hash) []byte
+
+
+// KeyValueWriter wraps the Put method of a backing data store.
+type KeyValueWriter interface {
+	// Put inserts the given value into the key-value data store.
+	Put(key []byte, value []byte) error
+
+	// Delete removes the key from the key-value data store.
+	Delete(key []byte) error
+}
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